有序数组的随机排列
问题描述
将一个有序数组随机排列，模拟扑克牌洗牌的场景。
这是我曾经面试到过的一个小算法题，今天整理出几种方法。
解决方法一：数组元素之间进行随机交换
数组有n个元素，那么就有n的阶乘中排列方法，代码如下：
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| NSMutableArray *arrCards = [[NSMutableArray alloc] initWithObjects:@"1",@"2",@"3",@"4",@"5",@"6",@"7",@"8",@"9", nil];
int i = 0;
int j = 1;
while (i<arrCards.count) {
j *= (i+1);
i++;
};
int k =0;
NSString *tmp;
int ran1 = 0;
int ran2 = 0;
while (k<=j) {
ran1 = arc4random() % arrCards.count;
ran2 = arc4random() % arrCards.count;
tmp= [arrCards objectAtIndex:ran1];
[arrCards replaceObjectAtIndex:ran1 withObject:[arrCards objectAtIndex:ran2]];
[arrCards replaceObjectAtIndex:ran2 withObject:tmp];
k++;
}
for (NSString *cardNum in arrCards) {
NSLog(@"%@",cardNum);
}
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解决方法方法二：自身随机插入
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| i = arrCards.count-1;
while (i) {
tmp = [arrCards objectAtIndex:i];
[arrCards removeObjectAtIndex:i];
[arrCards insertObject:tmp atIndex:ran1];
i--;
}
for (NSString *cardNum in arrCards) {
NSLog(@"%@",cardNum);
}
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